An automobile driver travels from a plane to a hill station $120 \ km$ distant at an average speed of $30 \ km/hr$. He then makes the return trip at an average speed of $25 \ km/hr$. He covers another $120 \ km$ distance on the plane at an average speed of $50 \ km/hr$. His average speed over the entire distance of $360 \ km$ will be:

  • A
    $\frac{30 + 25 + 50}{3} \ km/hr$
  • B
    $(30 \times 25 \times 50)^{1/3} \ km/hr$
  • C
    $\frac{3}{\frac{1}{30} + \frac{1}{25} + \frac{1}{50}} \ km/hr$
  • D
    None of these

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